Structural recirculation and refractory hypoxemia under femoro‐jugular veno‐venous extracorporeal membrane oxygenation

The performance of each veno-venous extracorporeal membrane oxygenation (vv-ECMO) configuration is determined by the anatomic context and cannula position. A mathematical model was built considering bicaval specificities to simulate femoro-jugular configuration. The main parameters to define were cardiac output (QC ), blood flow in the superior vena cava (QSVC ), extracorporeal pump flow (QEC ), and pulmonary shunt (kS-PULM ). The obtained variables were extracorporeal flow ratio in the superior vena cava (EFRSVC = QEC /[QEC + QSVC ]), recirculation coefficient (R), effective extracorporeal pump flow (Qeff-EC = [1 - R] × QEC ), Qeff-EC /QC ratio, and arterial blood oxygen saturation (SaO2 ). EFRSVC increased logarithmically when QEC increased. High QC or high QSVC /QC decreased EFRSVC (range, 68%-85% for QEC of 5 L/min). R also increased following a logarithmic shape when QEC increased. The R rise was earlier and higher for low QC and high QSVC /QC (range, 12%-49% for QEC of 5 L/min). The Qeff-EC /QC ratio (between 0 and 1) was equal to EFRSVC for moderate and high QEC . The Qeff-EC /QC ratio presented the same logarithmic profile when QEC increased, reaching a plateau (range, 0.67-0.91 for QEC /QC = 1; range, 0.75-0.94 for QEC /QC = 1.5). The Qeff-EC /QC ratio was linearly associated with SaO2 for a given pulmonary shunt. SaO2